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| author | Michael Strauss <michael.strauss@amd.com> | 2022-08-31 15:10:43 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-10-12 09:53:27 +0200 |
| commit | 4afcb53474aef6006ae6ce86f5aa09cd856563ba (patch) | |
| tree | 1945fe600a15d65abc254c55ba761d6424f33776 | |
| parent | 5e76ff629a201e920cfd6d4ec09432ec500256cb (diff) | |
| download | linux-stable-4afcb53474aef6006ae6ce86f5aa09cd856563ba.tar.gz linux-stable-4afcb53474aef6006ae6ce86f5aa09cd856563ba.tar.bz2 linux-stable-4afcb53474aef6006ae6ce86f5aa09cd856563ba.zip | |
drm/amd/display: Assume an LTTPR is always present on fixed_vs links
[ Upstream commit 29956d0fded036a570bd8e7d4ea4b1a1730307d2 ]
[WHY]
LTTPRs can in very rare instsances fail to increment DPCD LTTPR count.
This results in aux-i LTTPR requests to be sent to the wrong DPCD
address, which causes link training failure.
[HOW]
Override internal repeater count if fixed_vs flag is set for a given link
Reviewed-by: George Shen <George.Shen@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Michael Strauss <michael.strauss@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c index 6d5dc5ab3d8c..a6ff1b17fd22 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c @@ -3703,6 +3703,14 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link) lttpr_dpcd_data[DP_PHY_REPEATER_EXTENDED_WAIT_TIMEOUT - DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV]; + /* If this chip cap is set, at least one retimer must exist in the chain + * Override count to 1 if we receive a known bad count (0 or an invalid value) */ + if (link->chip_caps & EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN && + (dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt) == 0)) { + ASSERT(0); + link->dpcd_caps.lttpr_caps.phy_repeater_cnt = 0x80; + } + /* Attempt to train in LTTPR transparent mode if repeater count exceeds 8. */ is_lttpr_present = (dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt) != 0 && link->dpcd_caps.lttpr_caps.max_lane_count > 0 && |